1. Field of the Invention
The invention relates to a vibration damping control device that controls driving power (driving force or driving torque) of a vehicle, such as an automobile, that uses an engine as a driving device to suppress vibration of a vehicle body and, more particularly, to a configuration for managing the state of a throttle valve of the engine in vibration damping control.
2. Description of the Related Art
Vibration, such as pitch and bounce, during running of a vehicle occurs because of braking and driving forces (or inertial force) acting on a vehicle body during acceleration or deceleration of the vehicle or another external force acting on the vehicle body. Those forces are reflected on a “wheel torque” that is exerted on a road surface (torque acting between wheels and a contact road surface) by each wheel (driving wheel during driving). Then, in the field of vibration damping control for a vehicle, Japanese Patent Application Publications No 2004-168148, No. 2006-69472 and No. 2009-40163 (JP-A-2004-168148, JP-A-2006-69472 and JP-A-2009-40163) describe that wheel torque is regulated through driving power control over an engine or another driving device of the vehicle to thereby suppress vibration of a vehicle body during running of the vehicle. In the vibration damping control over vibration through driving power control, a movement model constructed by assuming a so-called mechanical model of sprung mass vibration or sprung and unsprung mass vibration of the vehicle body is used to estimate pitch and bounce vibration that occurs in the vehicle when acceleration or deceleration is required of the vehicle or when an external force (disturbance) acts on the vehicle body to cause the wheel torque to fluctuate, and then regulate the driving power of the driving device of the vehicle so as to suppress the estimated vibration. In the case of vibration damping control of this type, the source of force that generates vibration is regulated to suppress generation of vibration energy rather than generated vibration energy is absorbed and suppressed like vibration damping control through a suspension, so it is advantageous that vibration damping action is relatively quick and energy efficiency is high. In addition, in the vibration damping control as described above, a control target is narrowed to the wheel torque or the braking and driving force of each wheel, so it is relatively easy to regulate the control.
In the above vibration damping control through driving power control, the wheel torque is regulated so as to suppress pitch and bounce vibration of the vehicle, so the power of the driving device is frequently and vibrationally varied as compared with normal times. Particularly, when the vibration damping control is executed in a gasoline engine vehicle, an vibrational variation of the opening degree of a throttle valve is required to regulate the intake air flow rate of the engine. Thus, movable portions (for example, gear teeth, gear bearings, and the like) of the throttle valve frequently move. This may advance a change of state (hereinafter, referred to as “change of characteristic”) that causes a change of operating characteristic of the throttle valve, such as wear and thermal deformation of those movable portions, earlier than normal times. Thus, when a gasoline engine vehicle is equipped with the above vibration damping control device, it is necessary to manage the “change of characteristic” in such a manner that control operation is regulated so that the amount of wear, thermal deformation, or the like, of the movable portions of the throttle valve falls within a predetermined range (criteria) before the vehicle reaches the end of service life (management of the change of characteristic of the throttle valve). In addition, the change of characteristic, such as the degree of advance of wear or thermal deformation of the throttle valve movable portions due to operation of vibration damping control through driving power control depends on the condition of a running road of the vehicle. For example, on a bad road, as the vibration of the vehicle body increases, the amount and frequency of operation of vibration damping control increase. It is not appropriate to simply manage such change of characteristic on the basis of the travel distance or service age of the vehicle. For example, it is presumable that a certain limitation is set for the travel distance, service age of the vehicle or the operating time of the control and then operation of the control is prohibited when those limitations are exceeded. However, as is already described above, the degree of advance of wear or thermal deformation of the throttle valve movable portions depends on the condition of a running road. Therefore, there may be a case where the change of characteristic, such as the degree of wear or thermal deformation, has advanced to an allowable limit when the set limitation has been reached or a case where there is still a sufficient allowance up to the allowable limit. Thus, it is desirable that the change of characteristic of the throttle valve is managed directly on the basis of the degree of advance of wear of the throttle valve movable portions or the “change of another characteristic”.